The new owners of Llanishen Reservoir say they’ve yet to decide on their future plans for the drained beauty spot.

Campaigners last night called on the steel firm Celsa to start the process of refilling the heritage-listed structure as soon as possible.

It could take up to 10 years for the reservoir – formally a mecca for sailing in the capital – to be restored completely. Western Power Distribution (WPD) drained the reservoir in 2010 as the firm pursued plans to build 324 homes on the site.

The Spanish firm says its main concern was to “protect and maintain” the water supply from Lisvane Reservoir to its steelworks in Tremorfa.

Celsa UK’s head of human resources, James Ellis, yesterday said the company had not made any decisions about the future of Llanishen Reservoir.

“Our primary focus has been its acquisition for the water it [Lisvane Reservoir] supplies us,” Mr Ellis said. “Protecting and maintaining that supply has been our immediate goal so that we can continue to ensure the future sustainability of the steelworks and the employment it provides.”

He added: “In the meantime, we will need to evaluate the obligations that we have acquired under the environmental permit and those levied by the fact that Lisvane has Site of Special Scientific Interest status.”

Richard Cowie, chairman of the Reservoir Action Group (RAG), said it could take anything up to 10 years for rainwater to naturally refill Llanishen Reservoir.

One option to speed up the process, he said, would be to take water from the Nant Fawr stream. An online petition to start refilling has already been launched.

“We will be pressing them to refill it – and if they bought it for the water then we have both got the same aim really,” Mr Cowie said.

RAG is keen to meet Celsa to discuss their plans, as is Cardiff North’s Labour AM Julie Morgan, who yesterday wrote to the firm’s UK management.

Mrs Morgan said: “I want Celsa to refill the reservoir as soon as possible, it would be a huge boost to the local area and all of Cardiff.

“It’s a simple but lengthy process and there are fairly low costs involved. The place looks awful – it would be great for Celsa if they decided on an early refill.”